Keeping frost out of my canopy

[ETsC10]

I've got a fairly rattle-trap canopy...it doesn't leak but it's not air
tight. Has single pane windows both sides and a fairly loose
above-tailgate hatch in back.

My problem is it collects enough moisture inside that, now that its below
freezing, it ices up and makes visibility impossible. BTW-bed is empty
and has a plastic bed liner.

Tonight, it's 33° F and 58% humidity and they are clear now BUT in the
past week it's been down to 24° to 26° every night and then the ice on
the inside of the canopy's windows happens.


Any fixes? Can I wipe the inside glass with anything?
Lay trays of cat litter inside to dry it out? I'm thinking that litter
will finally get saturated and become a never-ending replacement
expense. I hate to go on a spending spree before some feedback.

Thanks for any recommendations.